This application claims priority to German patent application DE 101 01 138.5-16, filed on Jan. 12, 2001, the entire contents of which are incorporated herein by reference.
Interlocks for use in injection molding machines are known and are used especially in two-plate injection molding machines. Thus, DD 274 590, for example, describes an interlock which is directed toward a common intersection of the mid-perpendiculars of each of the respective contact surfaces of the claw bush and the piston and the rod point. The entire teachings of DD 274 590 are incorporated herein by reference.
U.S. Pat. No. 3,465,387 also discusses the problem of joining a rod or column of a two-plate injection molding machine to a second plate flexibly, but permanently. The overhung columns are guided in a fixed bearing and also in a second bearing disposed in a bush. This second bearing has limited flexibility due to the geometric shape of the bush. This flexible bearing and the masses of the overhung ends of the column cause the position of the column ends to deviate from their longitudinal axes when dipping into the high-pressure clamping cylinders. To compensate this, the clamping cylinders have a very complex structure. The interlock jaws are mounted movably in the hydraulic fluid inside the hydraulic fluid cell so that considerable deviations of the columns from their longitudinal axes can be compensated and so as also to assure that the interlock jaws will have the freedom of motion required by the bending of the plates during the build-up of the closure force. However, this multi-component structure of the cylinder is very expensive to produce. It is a complicated mechanism consisting of many individual parts, and thus prone to trouble. The entire teachings of U.S. Pat. No. 3,465,387 are incorporated herein by reference.
The proposed solutions have the disadvantage that the rod is supported in an expensive bearing and that the forces are transmitted to the rod at one point.
It is one aspect of the invention to offer a solution by which the forces are applied in a distributed manner, without significantly interfering with flexibility in the bearing.
In one embodiment, a claw bush has at least two stages, to apply the force in a distributed manner, the contour of the stages corresponding to the end of the piston rod and/or to the end of the column, the average radius of the first stage differing from the average radius of the second stage. This design achieves the result that the actual forces are transmitted on different levels. This holds both for their transmission to the column and also for the piston, but also for application of the force to the claw bush.
The two different stages can be doubled, that is, on the one hand, two stages which correspond to the column and whose two corresponding contours have different average radii and, on the other hand, two stages which correspond to the piston end and whose two corresponding contours have different average radii. The different average radii assure that the force flux acting on the first stage is applied to the column and to the piston respectively along another circumferential line than the force flux acting on the second stage. The two duplicate structures can be designed symmetrical.
It can be advantageous for the corresponding surfaces to make an angle with the center axis of the column. In some applications, the best force flux is achieved if the angle xcex1 is between 30xc2x0 and 60xc2x0, and in one embodiment, about 45xc2x0.
The cross-sectional form of the column and of the piston end can be any sensible and economically produced cross-section. A round cross section can be used, but a rectangular, octagonal, or, for example polygonal one can also be used.
The proposed solution can be suited for locking a closure unit of a two-plate injection molding machine for processing plasticized material.